The primary security means for protecting motor vehicles from theft or other unauthorised removal are door locks, steering locks and ignition locks. Many modern vehicles are also fitted with electronic immobilisers which prevent a computerised ignition and/or fuel injection system from working if a correctly coded key is used with the vehicle. However thieves have found ways to circumvent such devices by appropriate breakage of components of the vehicle and/or electrical interlinking, sometimes with sophisticated electronic devices carried to the vehicle by the thief.
Many types of mechanical immobilising devices are used as an adjunct to such primary vehicle security. These include bars clamped to steering wheels or gear change levers and clamps on road wheels. But clamps attached to the rims of steering wheels may be easily removed by using a bolt cutter to cut through the steering wheel rim, then bending open the rim, removing the lock, and bending the rim back into position for use in driving the vehicle away.
Many forms of lockable clamps have been developed which prevent rotation and removal of the road wheels. These tend to be more secure than steering wheel clamps but are larger, heavier and more awkward to transport and fit. For many people they are difficult to fit, and are inconvenient in the rain. They are also forcibly removable by a determined thief, particularly if they are not concerned about damaging the tires.